High speed flywheel

ABSTRACT

A high speed flywheel system for a vehicle, i.e. capable of running at speeds of 20,000 rpm or greater, the system comprising a flywheel mounted on a shaft and contained within a housing, and at least one bearing arrangement, wherein the bearing arrangement is mounted to the flywheel or the housing via an elastomeric component such as a ring and/or a metalastic bush, thereby to reduce NVH and prevent the resonant modes of the flywheel and housing interfering with one another.

This invention relates to flywheels, and particularly to a bearing system for a high speed flywheel system for use in a vehicle.

High-speed flywheels (e.g. those running at speeds of 20,000 rpm or more) for use as energy storage devices in hybrid vehicles are well known. One of the challenges presented by this technology is Noise, Vibration and Harshness (NVH). The flywheel is often at high speed (and therefore produces the most amount of noise) when the vehicle is at low speed or even stationary with the engine turned off.

Furthermore, although it is possible to separately design a flywheel and a flywheel housing each having no resonant modes within the flywheel operating speed range, when the two components are joined together, the interaction of the flywheel and the housing may produce a multi-body resonance which does occur in within the flywheel operating speed range.

An aim of the present invention is to reduce the effect of NVH on a hybrid system, and which ensures that the natural modes of the flywheel do not interfere with the natural modes of the housing and vice versa, thereby allowing full speed operation of the flywheel without producing damaging resonance.

Accordingly, the present invention comprises a flywheel as recited in claim 1 of the appended claims.

An advantage of the present invention is that the source of the vibration (the high-speed flywheel) is isolated from other parts of the hybrid system which may be excited by the vibration and therefore cause noise. Furthermore, the interaction of resonant modes of the flywheel and of the housing is prevented.

An embodiment of the present invention will now be described by way of example and with reference to the accompanying drawings in which:

FIG. 1 is a top view of a system in accordance with a first embodiment of the present invention,

FIG. 2 is a partial cross-sectional view of the system of FIG. 1;

FIG. 3 is a partial cross-sectional view showing the first bearing arrangement of the system of FIG. 1;

FIG. 4 is a partial cross-sectional view showing the second bearing arrangement of the system of FIG. 1;

FIG. 5 is a partial cross-sectional view showing a bearing arrangement in accordance with a alternative embodiment of the present invention;

and

FIG. 6 is a partial cross-sectional view showing a bearing arrangement in accordance with a further alternative embodiment of the present invention.

Referring to FIG. 2, the system 2 according one embodiment of the present invention comprises a flywheel 4, a shaft 6, and bearing arrangements 8, 10 located around the shaft on either side of the flywheel 4, i.e. the first bearing arrangement 8 is located on one axial side of the flywheel, and the second bearing arrangement 10 is located on the other side of the flywheel 4 with respect to the axis of the shaft. Each of the bearing arrangements 8, 10 comprises bearings 12 mounted in a race 36 which is fixed rigidly to the shaft 6. An outer diameter of the bearing race 34 is held in a bearing collar 14. The bearing collar 14 is isolated from the flywheel housing 30 by an elastomeric component comprising a first pair of stiff elastomeric rings 16, 18 which are formed of a flurocarbon material. The rings 16, 18 are contained within annular channels 32, 34 formed within bearing collar 14. Thus the rings 16, 18 are located radially outwardly of the bearings 12 with respect to the shaft 6.

The stiffness of the rings 16, 18 is sufficiently high such that in normal use of the system 2, the rings act to dampen any radial movement of the flywheel shaft 6, thus ensuring that the axis ‘A’ of the flywheel 4 does not move by more than a few microns. This ensures that a mechanical gear drive (not shown), which is connected to an end of the flywheel shaft 6, is maintained sufficiently close to its true centreline, thus ensuring correct operation of the gear drive and no contact between the periphery of the flywheel 4 and its housing 30.

The situation of the bearings 12 and elastomeric rings 16, 18 on either side of the flywheel 4 ensures that interaction of the resonant modes of the flywheel 4 and the housing 30 is prevented.

One of the bearing arrangements, 8, is restrained in both radial and axial directions with respect to the shaft 6. Axial restraint is provided by a further elastomeric component comprising a second set of elastomeric rings, comprising a pair of elastomeric rings 20, 22 (as illustrated in the right hand side bearing arrangement 8 of FIG. 2, and in detail in FIG. 4).

When the flywheel system 2 is in operation, the elastomeric components provide damping, thereby preventing NVH, and also preventing interaction of resonant modes of the flywheel and of the housing.

An oil transmission passage is provided by a channel 24 in the housing, and channels 26, 28 in the bearing collar 14, to allow a controlled feed of oil (not shown) for lubrication of the bearings. The size of the oil transmission passage, (i.e. the size of the channels 24, 26 and 28), is selected to provide a required damping coefficient of the assembly.

Although in the above embodiment, the elastomeric rings 16, 18 are formed of a flurocarbon material, they may be formed of any suitable elastomer, including natural rubber.

The elastomeric rings 16, 18 may alternatively be located radially inwardly of the bearings 12 with respect to the shaft 6, i.e. between the bearings 12 and the shaft 6.

In a system according to an alternative embodiment of the present invention, as illustrated in FIG. 5, the bearing arrangements, one of which(8′) is shown in FIG. 5, are mounted to the shaft 6 via a metalastic bush which comprises two concentric steel collars 42, 44 which are separated by an elastomeric component comprising a moulded rubber collar 46. In the embodiment of FIG. 5, the metalastic bush 40 is located between the bearings arrangement 8′, 10′ and the shaft 6′. However, the bush 40 may alternatively be located between the bearings 12 and the flywheel housing 30.

A further alternative embodiment, as illustrated in FIG. 6, may comprise a bearing arrangement 8″ comprising a metalastic bush 40 in combination with a first set of elastomeric rings 16, 18, and/or the second set of elastomeric rings 20, 22, thereby providing a greater degree of radial and/or axial damping. In the embodiment of FIG. 6, the elastomeric rings 16, 18 are located between the bearings 12 and the housing 30, and the bush 40 is located between the bearings 12 and the shaft 6. However, the locations of the bush 40 and the elastomeric rings 16, 18 may be reversed.

In the present embodiment, restraint of the bearing collar 14 is provided by a second pair of elastomeric rings 20, 22. However, in an alternative embodiment, the bearing collar 14 may be produced by moulding an elastomeric element and metal inner and outer rings as a single finished part. This alternative embodiment would be more suitable for mass production.

In further alternative embodiments, the first and/or second set of elastomeric rings may comprise a different number of rings. Furthermore, a second set of elastomeric rings 20, 22 may be provided on both bearing arrangements 8, 10, thereby providing axial restraint on both sides of the flywheel 4. 

1. A high speed flywheel system comprising a flywheel mounted on a shaft, and a housing, wherein two primary bearing arrangements are mounted to the flywheel system via elastomeric component located radially with respect to the shaft, and wherein one of the bearing arrangements is additionally mounted to the flywheel system via a second elastomeric component located axially with respect to the shaft; the system further comprising an oil transmission passage comprising a channel in the housing whereby oil can be fed to the bearings via the oil transmission passage.
 2. A high speed flywheel system as claimed in claim 1 wherein the primary bearing arrangements comprises bearings mounted in a race, wherein the system further comprises a bearing collar and wherein the first elastomeric component comprises a ring.
 3. A high speed flywheel system as claimed in claim 2, wherein the race is fixed to the shaft, and wherein the ring is located radially outwardly of the bearings with respect to the shaft, between the bearings and the housing.
 4. A high speed flywheel system as claimed in claim 2, wherein the ring is located radially inwardly of the bearings with respect to the shaft, between the bearings and the shaft.
 5. A high speed flywheel system as claimed in claim 2 wherein the first elastomeric ring is contained within annular channels provided in the bearing collar.
 6. A high speed flywheel system as claimed in claim 1 further comprising a bush comprising two concentric metal collars, wherein the first elastomeric component comprises a rubber collar located between the metal collars.
 7. A high speed flywheel system as claimed in the claim 6 wherein the bush is located radially outwardly of the bearings with respect to the shaft, between the bearings and the housing.
 8. A high speed flywheel system as claimed in claim 6, wherein the bush is located radially inwardly of the bearings with respect to the shaft, between the bearings and the shaft.
 9. A high speed flywheel system as claimed in claim 1, wherein the primary bearing arrangements comprise bearings mounted in a race, wherein the system further comprises a bearing collar and wherein the first elastomeric component comprises a ring; and wherein the race is fixed to the shaft, and wherein the ring is located radially outwardly of the bearings with respect to the shaft, between the bearings and the housing, and wherein the bush is located radially inwardly of the bearings with respect to the shaft, between the bearings and the shaft.
 10. A high speed flywheel system as claimed in claim 1 wherein the primary bearing arrangements comprise bearings mounted in a race, wherein the system further comprises a bearing collar and wherein the first elastomeric component comprises a ring; and wherein the ring is located radially inwardly of the bearings with respect to the shaft, between the bearings and the shaft, and wherein the bush is located radially outwardly of the bearings with respect to the shaft, between the bearings and the housing.
 11. A high speed flywheel system comprising: a flywheel mounted on a shaft, and a housing, wherein two primary bearing arrangements are mounted to the flywheel system via at least one first elastomeric component located radially with respect to the shaft, and wherein one of the bearing arrangements is additionally mounted to the flywheel system via a second elastomeric component located axially with respect to the shaft; and an oil transmission passage comprising a channel in the housing whereby oil can be fed to the bearings via the oil transmission passage; wherein the first elastomeric component and the second elastomeric component are separate components.
 12. A high speed flywheel system as claimed in claim 1 wherein the second elastomeric component comprises an elastomeric ring.
 13. A high speed flywheel system as claimed in claim 1 wherein each elastomeric component is formed of a fluorocarbon material or natural rubber.
 14. A primary bearing arrangement for use in a high speed flywheel system comprising a flywheel mounted on a shaft, and a housing, said primary bearing arrangement comprising: at least one first elastomeric component mounted to the flywheel system and located radially with respect to the shaft; at least a second elastomeric component additionally mounted to the flywheel system and located axially with respect to the shaft separately from the first elastomeric component; and an oil transmission passage comprising a channel in the housing whereby oil can be fed to the bearings via the oil transmission passage;.
 15. (canceled)
 16. A high speed flywheel system as claimed in claim 3 wherein the first elastomeric ring is contained within annular channels provided in the bearing collar. 